JPH03131716A - Linear position detector - Google Patents

Abstract

PURPOSE:To obtain the linear position detecting device which is not affected by the magnetization of the magnetic part of a magnetic scale by adding a degausser at a specific position. CONSTITUTION:The degausser 40 is provided at a position which is in the moving direction of a magnetic sensor element 40 and almost circumscribed with the linear position detecting device. Consequently, even if the magnetic part 11 of the magnetic scale 10 is magnetized, the degausser 40 erases the magnetism of the magnetism part before a magnetic sensor 30 performs detection. Consequently, the detection output is not affected by the magnetism. Thus, the linear position detecting device which is not affected by the magnetization of the magnetic part of the magnetic scale is obtained.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a linear position detection device.

[Conventional technology] The conventional technology will be explained with reference to FIG.

A magnetic scale 10 having a periodic pattern on its surface consisting of a magnetic part 11 and a non-magnetic part 12, and an excitation part provided opposite to the periodic pattern and for applying a bias magnetic field to the magnetic scale 10. A linear position detection device comprising a device 20 and a magnetic sensor element 30 provided between the magnetic scale 10 and the excitation device 20 and provided in contact or non-contact with the magnetic scale 10. Various types of devices are known. For example, some magnetic scales 10 have an uneven pattern on their surface. In this case, the magnetic part 11 refers to the space of the concave part, while the non-magnetic part 12 refers to one of the convex parts, for example, the base material. In addition, in the above structure, a structure in which the recessed portion is separately filled with a nonmagnetic material is also known. Still another configuration is one in which the surface of the base material is periodically altered to have different magnetic permeability. The excitation device 20 is known to use a permanent magnet or a solenoid coil.

This excitation method also includes DC excitation and AC excitation.

Known magnetic sensor elements include semiconductor elements such as Hall elements and magnetoresistive elements, and ferromagnetic magnetoresistive elements.

[Problems to be Solved by the Invention] However, in the conventional linear position detection device described above, the magnetic portion of the magnetic scale is non-uniformly magnetized due to, for example, external mischief, and as a result, the detection accuracy of the magnetic sensor element is reduced. The problem is that it decreases.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, it is an object of the present invention to provide a linear position detection device that is not affected by the magnetization of the magnetic portion of a magnetic scale.

[Means for Solving the Problems] To achieve the above object, a linear position detection device according to the present invention will be described with reference to FIG.

A magnetic scale 10 having a periodic pattern on its surface consisting of a magnetic part 11 and a non-magnetic part 12, and an excitation part provided opposite to the periodic pattern and for applying a bias magnetic field to the magnetic scale 10. A linear position detection device comprising a device 20 and a magnetic sensor element 30 provided between the magnetic scale 10 and the excitation device 20 and provided in contact or non-contact with the magnetic scale 10. In the apparatus, a demagnetizing device 40 is provided at a position in the moving direction of the magnetic sensor element 30 and at a position substantially circumscribing the linear position detecting device.

Furthermore, in the above configuration, the demagnetizing device 40 may be a magnetizing device 50.

[Function] According to the structure of claim 1, even if the magnetic part 11 of the magnetic scale 10 is magnetized, the demagnetizing device 40 demagnetizes the magnetized part before the magnetic sensor element 30 detects it. Since it is demagnetized, the detection output is no longer affected by magnetization. According to the structure of claim 2, even if the magnetic parts 11 of the magnetic scale 10 are magnetized, the nine magnetizing devices 50 detect that all the magnetic parts 11 of the magnetic scale are the same before the magnetic sensor element 30 detects the magnetic parts 11 of the magnetic scale 10. Because it is magnetized by a magnetic field,
The influence of magnetization caused by the previous accident is eliminated.

As a result, there is no variation in detection. In the configuration of claim 2, the bias magnetic field for detection by the excitation device 20 needs to be greater than the bias magnetic field applied to the magnetic section 11 by the magnetizing device 50. Further, it is desirable that the bias magnetic field applied to the magnetic part 11 by the first magnetizing device 50 is greater than or equal to the coercive force of the magnetic part 11, and in this case, the same idea as above is used.

The bias magnetic field for detection by the excitation device 20 is applied to the magnetic part 11.
It must be greater than the saturation magnetic field of .

[Embodiment] An embodiment of claim 1 is shown in FIGS. 1 to 3. First, explanation will be given with reference to FIG. Magnetic scale 10 is SCM4
It is a 35H plate material. This magnetic scale IO has recesses with a pitch of 1 mm, width of 1 mm, and depth of 0.1 mm periodically provided on the surface, the recesses filled with Cr, and finally the entire surface is plated with Cr to a thickness of 50 μm. . Such a magnetic scale 10 i:oi''(,';!i The magnetic part 11 is the base material SCM435H, and the non-magnetic part 12 is the Cr concave part.
It is. The excitation device 20 has a permanent magnet 21 with a length of 20 mm, a width of 10 mm, and a thickness of 5 mm, and a permanent magnet 21 with a length of 75 mm and a width of 10 m.
20 mm permalloy from both ends with a thickness of 1.5 mm.
It is constructed by being housed in a yoke 22 which is bent at right angles by mm. Both ends of this yoke 22 are installed to face the surface of the magnetic scale 10. The magnetic sensor element 30 is a ferromagnetic magnetoresistive element made by depositing permalloy on a glass substrate. Magnetic sensor element 30
forms a four-element bridge on the substrate. This magnetic sensor element 30 is located within the yoke 22 and between the magnetic scale 10 and the magnetic scale 10 so as to detect leakage magnetic flux of the magnetic scale 10. In this embodiment, the distance from the conventional linear position detection device having such a configuration is 2 mm in the movement detection direction.
A demagnetizing device 40 is provided at a remote location. As shown in FIG. 1, which is an X view of FIG. 2, this degaussing device 40 is constructed by bending silicon steel with a length of 56 mm, a width of 3 mm, and a thickness of 2 mm at a right angle by 20 mm from both ends of the yoke. It was constructed by winding a coil with a length of 10 mm and a number of turns of 200. The excitation current to this coil is I
Ap-p and frequency are 100Hz. The effects of this embodiment will be explained with reference to FIG. FIG. 3 is a characteristic graph showing the effects of the demagnetizing device 40 in the example and a comparative example in which the demagnetizing device 40 of the example is removed. In the same graph, P indicates the range that has been magnetized in advance by rubbing the magnetic scale with a permanent magnet, line A1 indicates the characteristics of the example, and line B
1 shows the characteristics of a comparative example. As can be seen from the same graph,
In Example A1, the waveform is regular, but in Comparative Example B1, which is a conventional technique, the waveform is distorted at the magnetized portion P. In other words, in the conventional configuration, when the magnetic part of the magnetic scale is magnetized, the comparator cannot output that part as a rectangular wave, but according to this embodiment, the degaussing device 40 can detect it without any trouble. I understand. Next, an embodiment of claim 2 will be described with reference to FIGS. 4 and 5. In FIG. 4, a magnetic scale 10, an excitation device 20,
The conventional linear position detecting device comprising the magnetic sensor element 30 has the same configuration as the conventional linear position detecting device of the embodiment of claim 1 described above. Therefore, the magnetizing device 50 was installed at a distance of 2 mm from the conventional linear position detection device in the moving direction. Note that this magnetized portion N50 has a width of 10 mm.

15m high on a silicon steel plate with a thickness of 2mm and a height of 20mm
It is constructed by winding a coil with a number of turns of 150 within a range of m. The effects of this embodiment will be explained with reference to FIG. Fifth
The figure shows a case where the magnetizing device 50 of the embodiment is operated over the entire region (A2) and a case where the magnetizing device 50 of the embodiment is operated in the middle of the magnetic scale, which has been magnetized in advance with a permanent magnet over the entire region. Magnetizing device 5 in the case where the operation is stopped (B2)
It is a characteristic graph showing the effect of 0. As can be seen from the graph, by continuing to operate the magnetizing device 50, the waveform of the detection output appears periodically (A2). In contrast,
In a comparative example where the operation of the magnetizing device 50 is stopped midway, the output waveform Q after the stop is affected by the previous magnetization and is distorted (B2). In other words, in the conventional configuration, when the magnetic part of the magnetic scale is magnetized, the comparator cannot output the magnetized part as a rectangular wave, but according to this embodiment, the magnetizing device 50 can detect it without any problem. I know that I can do it. As another embodiment, if the detection direction is the reciprocating direction, two demagnetizing devices or two magnetizing devices are installed between the conventional linear position detecting devices.

[Effects of the Invention] As explained above, the linear position detecting device according to the present invention has a configuration in which a degaussing device or a magnetizing device is added to a conventional linear position detecting device, so that the magnetic part of the magnetic scale is not attached. Even if the magnet is magnetized, nine positions can be detected with high precision without being affected by this effect.

[Brief explanation of the drawing]

Fig. 1... A block diagram of a degaussing device in an embodiment of the linear position detecting device of claim 1. Fig. 2... A block diagram of an embodiment of the linear position detecting device in claim 1. Figure f: J3... Claim Graph showing the effects of the embodiment of the linear position detection device of claim 1. Figure 4. Block diagram of the embodiment of the linear position detection device of claim 2. Figure 5. Implementation of the linear position detection device of claim 2. Graph 10 showing the effect of the example... Magnetic scale 11... Magnetic part 12... Non-magnetic part 20... Exciter 30... Magnetic sensor element 40... Demagnetizing device 50... Magnetizing Apparatus Figure 1 1U Figure 2 Figure 4

Claims (2)

[Claims] (1) A magnetic scale 10 having a periodic pattern on its surface consisting of a magnetic part 11 and a non-magnetic part 12, and a part provided facing the periodic pattern and for applying a bias magnetic field to the magnetic scale 10. excited device 20
and a magnetic sensor element 30 provided between the magnetic scale 10 and the excitation device 20 and provided in contact or non-contact with the magnetic scale 10. , the magnetic sensor element 3
A linear position detecting device characterized by having a demagnetizing device 40 at a position in the moving direction of zero and at a position substantially circumscribing the linear position detecting device. (2) The linear position detection device according to claim 1, wherein the demagnetizing device 40 is a magnetizing device 50.